# Thread: [SOLVED] Convert polar coordinates to rectangular

1. ## [SOLVED] Convert polar coordinates to rectangular

1. $r=-3*sintheta$
2. $r*sectheta=3$

How do you make these into rectangular equations?

2. Originally Posted by bilbobaggins
1. $r=-3*sintheta$
2. $r*sectheta=3$

How do you make these into rectangular equations?
1. $r = - 3 \sin \theta \Rightarrow r^2 = -3 r \sin \theta$ ......

2. $r \sec \theta = 3 \Rightarrow \frac{r}{\cos \theta} = 3 \Rightarrow r = 3 \cos \theta$. Now use what you've learned from how I did 1.

3. Originally Posted by mr fantastic
1. $r = - 3 \sin \theta \Rightarrow r^2 = -3 r \sin \theta$ ......

2. $r \sec \theta = 3 \Rightarrow \frac{r}{\cos \theta} = 3 \Rightarrow r = 3 \cos \theta$. Now use what you've learned from how I did 1.
I had already gotten to where you did in 2. 1 is still troubling me though, so you just multiplied both sides by r?

4. Originally Posted by bilbobaggins
I had already gotten to where you did in 2. 1 is still troubling me though, so you just multiplied both sides by r?
That's what I did in 1, right? And after doing this, is it obvious what comes next?

5. Originally Posted by mr fantastic
That's what I did in 1, right? And after doing this, is it obvious what comes next?
x^2+y^2=-3y?

6. Originally Posted by bilbobaggins
x^2+y^2=-3y?
(number 1, I assume)